Iceproof windshield



Oct. 9, 1945. w. J. O'CONNOR ICE-PROOF WINDSHIELD 2 Sheets-Sheet 1 FiledNOV. 12, 1941 |NVEN'1"OR Walter J 0 Conn a?" Oct. 9,1945. w. J. OCONNORICE-PROOF WINDSHIELD Filed NOV. -l2, 1941 2 Sheets-Sheet 2 INVENTORWalter I 0 T012710]- Patented Oct. 9, 1945 UNITED STATES PATENT OFFICEICEPROOF WINDSHIELD I Walter J. OConnor, Pittsburgh, Pa. ApplicationNovember 12, 1941, Serial No. 418,738

9 Claims.

This invention pertains to Windshields for vehicles of various typesincluding automobiles and locomotives and for airplanes, and is for awindshield of the type in which provision is made for the circulation ofheated fluid between the spaced sheets of glass for the purpose ofpreventing the accumulation of ice on the exterior of the windshield andthe formation of frost on the interior.

While the invention is applicable to various types of vehicles, it isespecially applicable for use on airplanes, particularly those intendedto fly at high altitude, where the accumulation of ice on the windshieldpresents a difficult problem, and where at the present time anti-freezesolutions are sprayed over the exterior of the windshield to preventicing.

It has heretofore been proposed to form windshields having spaced lightsof glass with an intervening body of fluid, but for various reasons suchdevices are not satisfactory for the use for which they are intended,and they are especially unsatisfactory for use on aircraft. In the firstplace many available fluids for use in the windshield have an index ofrefraction different from that of glass, or are less conductive to lightthan glass or air. Consequently it is desirable that the space betweenthe two sheets of glass be relatively thin in order that the fluid willnot unnecessarily obstruct the vision or refract light. Also formilitary planes which make violent manoeuvres at high speeds it isdesirable'that the Volume of fluid be maintained relatively small incomparison with the thickness of the glass, in order to avoid unduestrains when the course of the ship is suddenly changed. Windshields asheretofore constructed, using a heated fluid to prevent the formation ofice, depend upon the establishment of convective currents in the body ofthe fluid between the two sheets of glass. They contemplate, forexample, the provision of heating means at the bottom of the windshieldfor heating the fluid, so that it may rise between the two sheets ofglass and displace the colder fluid which lies above. The difiicultywith this arrangement is that if the intervening fihn of liquid isrelatively thin, the overlying fluid blocks the warmer fluid fromrising, so that only a small portion of the windshield is kept clear ofice. Moreover such circulation as takes place cannot be controlled, andthe field of vision of the pilot or opera-tor is through a liquid inwhich there are oppositely moving currents of fluid of differentdensities. Moreover, at high altitudes especially, boiling of the liquidin contact with heaters may take place, causing the field of vision tobe distorted by bubbles generated in the fluid.

The present invention is designed to eliminate these defects and toprovide a controlled unidirectional circulation of the fluid in thefield of vision with no possibility of bubbles circulating across thefield of vision, and provides a windshield which permits a relativelythin film or body of fluid to be used between the separated lights ofglass. The invention further provides a novel construction for theassembly of windshields of this character, and includes various otherprovisions to adapt the construction to use on aircraft where widechanges of atmospheric pressure are encountered, and to meet thepossibility of the plane flying at times in an inverted position.

The invention may be more fully understood by reference to theaccompanying drawings, in which Figure 1 is a transverse verticalsection through a windshield embodying my invention;

Figure 2 is a view partly in elevation and partly in section, showingthe windshield as viewed by the operator;

Figure 3 is partly a side elevation and partly a section of thewindshield shown in Figure 2;

Figure 4 is a longitudinal vertical section through a slightly modifiedform of windshield; and

Fig. 5 is a transverse vertical section across a windshield generallysimilar to that shown in Fig. 4, but wherein there are one or moreextensions on the frame to provide filling openings.

Referring first to the form of invention illustrated in Figures 1-3inclusive, the windshield is preferably constructed of a metal framecomprising an outer member 2, havin an inwardly turned flange 3 and anoutwardly turned flange 4. For securing the most advantageouscirculation of fluid and the avoidance of spaces in which there islittle circulation, the windshield is preferably circular, but it may beelliptical, or in the form of a square with rounded corners, or invarious other shapes. For the purpose of illustration, however, it isillustrated as being round, this being the most efficient shape. Withinthe outer frame member 2 and spaced therefrom is an inner annular framemember 5, having an inwardly turned flange 6 which lies inside theflange 3, and an outwardly turned flange I that overlaps the flange 4.This construction of the two frame members provides a frame with aninternal annular fluid-circulating passage 2a formed therein, the innerand 'outer walls of which passage are constituted by the members 2 and5, and the side walls of which are constituted by the flanges 3 and 1.The two main frame members 2 and 5 may be secured together in anysuitable manner, as by havin the contacting flange portions 3 and 6 and4 and 1 welded, forming a liquid-tight joint.

The overlapping flanges 3 and 6, which extend inwardly, form an annularledge or lip against which the inner sheetof glass designated 8 is set.Around the peripheral edge of the sheet of glass there may be a suitablyformed packing ring made of metal or synthetic rubber or any othersuitable composition, this ring of packingv being designated as having aU-shaped crosssection and marked 9 in the drawings.

Set inside the frame against the sheet of glass 8 is a spacing ring I0,preferably in the form of a channel-shaped annulus of light sheet metalhaving the flanges thereof turned outwardly to contact the inner wall offrame member 5. This spacing ring serves to hold the sheet of glass 8tight against the inwardly turned flange 3-45. A second sheet of glassII is set into the frame and is held in spaced relation to the firstsheet by the spacing ring II), this spacing ring I0 hold ing the sheetof glass 'll substantially fl-ush'with the face of the annulanframe.The-sheet of glass H in turn is held in place by a ring or annulus I2,which is bolted to the flange formed by the projecting, overlappingedges of the flanges 4 and 1. A packing ring 9 also surrounds theperipheral edge of the sheet of glass II and is similar to the packingring 9 on the sheet of glass 8. The windshield thus comprises a metalframe havin a channel 211 around its periphery and, with afluid-circulating space l3 between the two sheets of glass 8 and H, thespace I3.

between the sheets of glass being separated from the annular channel inthe frame.

At the bottom of the windshield the space l3 opens into the annularpassage 2a through a plurality of openings l4, these openings beingbetween the top and the bottom of the window, a thermo-syphoncirculation can be maintained across the field of vision whether thewindow is inverted or is in an upright position.

At the top of the frame there is shown a filling spout H) with aremovable cap 20. Leading from a point immediately over the cap is anoverflow pipe 2| that rises to a point higher than the top of the cap,and then turns back in the reverse direction and its lower end Zla, asshown in Figure l, is below the bottom of the windshield. This pipeallows the fluid in the windshield to expand upon being heated andprevents the gen- .eration of undue pressure in the windshield. At

the same time because of the length of the pipe fluid cannot run out ofthe pipe even when the plane is flying in an upside-down position,unless there is a pressure within the windshield to force it out. Thepipe 2| also serves as a vent to relieve any gases or entrained airwhich may be released from the fluid when it is heated.

The outwardly projecting flange on the frame formed by the overlappingflanges 4 and 1- of the two frame members 2 and5 provides'a support forattaching the windshield into the fuse-- lage of the plane, or into thevehicle or craft on which it is mounted.

The frame itself may be of relatively light construction and it can bereadily assembled. The space l3 between the two sheets of glass may berelatively thin as compared'to the overall dimensions ofthe windshield,and in this respect the drawings must not be construed as necessarilyshowing the best proportions, as the thickness of the chamber 13 may bevaried upon experimentation to determine the most efficient proportionsand the most desirable velocity for the circulation of the fluid. Theliquid circulates under a thermo-syphon action; all of the liquid 46moving across the plane of vision is flowing downwardly. All of theuprising currents are formed both in the spacer Ill and in the portionof the frame member 5which provides the inner wall of the passage.Similarly openings l5 at the top of the frame establish communicationbetween the space l3,and the channel 2a.

Mounted on the inner face of the frame of the windshield at eachv sidethereof are one or more, preferably several, electric heating elements16, having terminals I! at the inner face of the frame to which currentsupply wires may be attached. Heaters of this kind are well known tothose skilled in the art, and arefrequently referred to as immersionheaters. The heaters extend only intothe passage 2a and serve to heatthe fluid in this passage. The heating of the fluid in the passageoccurs only at the sides of the frame. (This results in the setting upof a thermo-syphon circulation of the fluid which fills the space,between the two panes of glass and which also fills the channel or duct2a. The fluid upon becoming heated ,circulatestoward the top of theframe where it flows throughthe openings l5 into the space l3 betweenthe two panes of glass, displacing the colder fluid which flows outtheopenings l 4 and which flows in each direction from the bottom of theframe up toward the heaters. For controlling the temperature of thefluid a thermostat I8 is located in the duct 2a at the very bottom ofthe frame, where it is responsive to the coolest fluid in thewindshield. Because of the disposition of the heating elements entirelyin the side channels or ducts in the ducts or channel provided in theframe of the 'windshield. Uniform heating of the surface of the glass istherefore assured. Any gas bubbles that mightbe generated due to theheating of the fluid, particularly at the low pressure encountered athigh altitudes, will flow through the ducts to the vent pipe 2|, andnone of these bubbles will circulate across the field of vision.

Figs. 4 and 5 illustrate modifications which are generally similar tothe windshield previously described but wherein I have illustrated aprovision for heating the fluid by means of heateXchange coils iminersedin the fluid, and through which hot oil from the crank cases of theairplane engines, hot water from the radiatorsof the engines of theplane or-motor vehicle, or steam in the case of a steam locomotive, mayflow in lieu of using electric heaters. In the windshield shown in theseviews the frame itself is of a generally rectangular shape, but thefield of vision defined by the glass plates is circular. In both Figures4 and 5 the general construction is substantially the same, the onlydifference being in the disposition of the expansible and compressibleelements hereinafter referred to, and like reference numerals havetherefore been used to designate the corresponding parts. The frame isconstructed similarly to the one described in connection with Figures1-3, there being an outer sheet metal frame member25 having a longinwardly turned flange 26 and a short outwardly turned flange 21. Thereis an inner frame member 28, having a short inwardly turned flange 29and a long outwardly'turned' flange 30. The overlapping flanges 21 and30 are welded together to form a unitary, outwardly turned flange, andthe overlapping portions of the flanges 28 and 29 are welded together toform an inwardly turned flange against which the inner light of theglass 3| is held. At 32 is a spacer, similar to the spacer I 0, and 33designates the outer sheet of glass which is confined against the spacer32 and by an annulus 34 bolted to the exterior of the frame of thewindshield. The space 35 between the two sheets of glass is completelysurrounded by the member 28 and outside the member 28 and inside themember 25 is a fluid-receiving chamber 36. Instead of this chamber beingin the form of an annular duct, as described in connection with Figures1, 2, and 3, it is in the form of a rectangle around the circular fieldof vision. However, it confines the circulation of fluid in the same wayas described in connection with the first three figures. In order toassure proper directional circulation of the fluid, holes 3! lead fromthe space 36 into the space 35 between the two sheets of glass at thetop of the windshield. Similar holes 38 lead from the space 35 into thelower part of the space 36. There are curved baille plates in the lowerpart of the space 36, these baflle plates being designated 39, and theyextend from a point about half way up the windshield downwardly to acentral discharge pipe 40. There are vertical baflle plates at 4|. In aplane above the vertical bafile plates 4|, the bafiie plates 39 areprovided with openings 42 for the upwardly circulating fluid. Thedownwardly circulating fluid is discharged through the pipe 40 into thespace at each side of the frame under the bafiles 33. In the space 36under the bailles 39 are heat transfer coils 43. As previouslyindicated, hot oil, water, or steam may be circulated through lthesecoils, depending upon the character of vehicle on which the windshieldis mounted. This type of heater is particularly desirable for aircraft,as it may substantially reduce the area now required for water-coolingradiators on liquid-cooled engines, or it may be used to replaceradiators for cooling the crank case oil, which are now sometimesrequired for aircraft use.

A thermostat 44 may be provided in the discharge pipe 40 for controllingthe temperature to which the liquid in the windshield is heated. Hereagain the thermostat is located where it contacts the coolest fluidflowing through the windshield and assures of all liquid being heated toa temperature high enough to eliminate completely ice or frost on thesurface of the windshield.

At the top of the frame, as shown in Figure 5, there is a fillin spout45 with a cap 46. In Fig. 4 the spout 41 is omitted, there merely beingfillin openings in the top of the shell. In order to relieve thepressure caused by the expansion of the fluid, with-out, however,providing any overflow, a Sylphon bellows 41 may be secured to the undersid of the filling cap with the interior of the bellow opening toatmosphere through an opening 48. In addition to the Sylphon bellowsused in the filling cap, or in lieu thereof, one or more such bellowsmay also be mounted in the top of the exterior frame member 25, as shownat 49 in Figure 4. These bellows open to the atmosphere the same as thebellows shown in Figure 5. When the liquid in the windshield expandsupon being heated, thus creating a pressure, the Sylphon bellowscollapse and accommodate the expanded volume of fluid without thegeneration of excessive pressure in the windshield. When the fluid inthe windshield cools, the bellow expand. This arrangement is preferableunder some circumstances to the one shown in Figures 1, 2, and 3, forthe reason that there is no escape of the liquid from the windshield,and once the windshield has been filled and entrained air has beeneliminated the device will operate for long periods of time withoutrefilling. At the same time the expansion and contraction of the bellowsallow the fluid to expand, but the windshield is entirely full of liquidat all times, so that there will not be bubbles to interfere withvision.

In both constructions there is a unidirectional flow of fluid across thefield of vision maintained entirely by thermo-syphon action, and in eachform the device is adapted for use on airplanes, which are subject towide ranges of atmospheric pressure. It will, of course be apparent thatthe overflow arrangement of Figure 1 might be used on the windshield ofFigure 4, or the Sylphon bellows of Figures 4 and 5 can be used in theconstruction shown in Figure 1.

While I have illustrated and described certain specific embodiments ofmy invention, it will be understood that this is by way of illustrationand that various changes and, modifications may be made within thecontemplation of my invention and under the scope of the followingclaims. Also th term glass as used herein is intended to comprehendother transparent sheet material as, for example, transparent plasticmaterials.

I claim as my invention:

1. A windshield construction comprising an outer metal frame memberhaving a long internal flange on one edge and a short external flange onthe other edge, an inner frame member having a short internal flangethat contacts the internal long flange of the first member and a longexternal flange on its other edge contacting the short external flangeof the first member, the contacting flange portions of the two membersbeing joined to make fluid-tight seams, a sheet of glass abutted againstthe internal lip formed by the contacting internal flanges, a secondsheet of glass in the frame spaced from the first, and an annularretaining member holding the second sheet of glass in the frame, theframe thus constructed providing a fluid-circulating space between theinner and outer members, the inner frame member having oppositelypositioned ports opening into the space between the two sheets of glass.

2. A windshield construction comprising an outer metal frame memberhaving a long internal flange on one edge and a short external flange onthe other edge, an inner frame member having a short internal flangethat contacts the in ternal flange of the first member and a longexternal flange on its other edge contacting the short external flangeof the first member, the contacting flange portions of the two membersbeing joined to make fluid-tight seams, a sheet of glass abutted againstthe internal lip formed by the contacting internal flanges, a secondsheet of glass in the frame spaced from the first and an annularretaining member holding the second sheet of glass in the frame, theframe thus constructed providing a fluid-circulatin space between theinner and outer members, the inner frame member having openingstherethrough at the top and bottom of the frame to provide for thecirculation of liquid from the space in the frameto the space :betweenthe glass sheets, and;

heating means in the said space within the frame.

ing. a shortv internal flange thatcontaets the internal long flange ofthe first member and a long external flange-on its other edgecontacting;

the short external flange of 1 the first member, the contacting flangeportions of the two membersbeing joined to make fluid-tight seams, asheet of glass abutted against the internallip formed by the contactinginternal flanges, asecnd sheet of glass in the framespaced from thefirst, an annular retaining member holding the second sheet of glass inthe. frame, the frame thus; constructed providing a fluid-circulatingspace between the inner and outer members, the inner frame member havingoppositely posi' tionedports opening into the space between the twosheets of glass, and compressible means mounted in the framefor-relieving pressure-in the windshield createdby the expansion of theliquid, e g

4. A windshield construction comprising an outer metal frame memberhaving a :longinternal fiange onrone edgeand ashort externalv flange 1onathe, otheredge, an inner frame member having ashort internal-flange.that contacts the internal long flange of the first member and a longexternal flange on its other edge contacting the short external flangeof the first member, the contacting flange portions of the two membersbeing, joined to make fluid-tight seams, a sheet of glassabutted againstthe internal lip formed by the contacting internal flanges, a secondsheet of glass in the frame spaced from the first, an annular retainingmember holding, the second sheet of glass inthe frame, the frame thusconstructed providing a fluid-circulating space between the inner andouter members, the inner frame member having oppositely positioned portsopening into, the space between the two sheets of glass, and a Sylphonbellows mounted on the frame and immersed in the fluid with its interioropeningto atmosphere to compensate for changes in the volume of. theliquid in the windshield and frame ,with changes of temperature.

5. A windshield comprising a hollow frame defining an ,open field ofvision, spaced transparent sheets over the open field of vision forminga window and, with the frame, providing a fluid receiving space betweenthe transparent sheets, the hollow frame forming a peripheral ductentirely around the window, the frame having a series of ports thereinacross the top and across the bottom of the window establishingcommunication between the peripheral duct and the space between thetransparent sheets, and heating means in the duct for liquid ateach sideof the window entirely intermediate the top and bottom whereby athermo-syphon circulation of liquid ass sea may; be maintained when thewindow ,is come pletely inverted.-

6. Aewindshield comprising a hollow framedefining an openfield ofvision; spacedrtransparent.

sheets over the Open field of'vision forming a window, and, with theframe, providing a fluid receiving space between the transparentsheets,. the hollow frame forming a peripheral duct entirel -around thewindow, the frame having. a,

series of separated portstherein across the top:

and bottom of the window establishing communi cation between theperipheral ductand the spacebetween the transparent sheets, heatingmeans in the duct for liquid at each side of the window entirelyintermediate the top and'bottom whereby athermo-syphon circulationofliquid. may be maintainedwhen the window is completely in:

verted, and means: providing for the expansion.

and contraction of c the liquid adapted to prevent spilling when thewindow is inverted. I

'7. A windshield comprising a hollow-frame de'r fining an open'field :ofvision, spaced transparent sheets, over'the open field of visionforminga window. and; with the frame, providing a fluid,

receivingzspace between the transparent sheets;

the hollow frame forming a'peripheral'duct en tirely around the window,the framehavin-g a series of-ports therein across: the top'and bottom ofthe window establishing communicationibetween the peripheral ductand thespace-betweenthe transparent sheets, and heating meansin the ductiforliquid at each side of the window, .an-d

an'expansible andcontractable member in the duct responsive. to pressureof liquid in the ductto compensate for expansiomand con-tractionof theliquid under heating andcooling and-while maintaining the liquid underpressure.

8; A windshield comprising a frame having. spaced'transpa-rent sheetsproviding. a window witha fluid receiving spacebetween the trans parentsheets, a liquid circulatingsystem including passageways andheating-means for main taining a thermo-syphon circulation ofliqu-id.

fromrthebottomaof the space externally-thereof.-

the: window and acrossthe-top: of the window only at'the middle thereofand for a distanceextending each side of the middle, and means formaintaining a thermo-syphon circulationof WALTER J OCONNORF

